As fish evolved into land-living animals, they had to change their body form. Water supports the body, but on land the animals needed to evolve a strong spine and ribs to stop their body from collapsing. They needed to develop muscles to support the body and to move the limbs. New bone structures had to evolve to support the limbs. Other changes were the perfection of lungs for breathing air, and sense organs, which would work well on land. Despite adaptations, these animals still needed to keep moist and to return to the water to breed. They are known as amphibians, which means ‘living on land and in water’.
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